Gonna see if I can ask this question correctly:
A phono cartridge can change how a vinyl record sounds quite significantly. But if I have to choose between upgrading to a high end cartridge or to a high end stereo, which will make a more noticeable difference and how?
Now with CD’s, what would greatly alter the sound the most? The player or the stereo?
The speakers are also at play in this and even wires and all the pieces like pre-amps, etc. when I’m asking this question.
But what singular piece of equipment can effect how something sounds, and will it change from source to source (cd’s, vinyl, digital, etc.)?
For records its the cartridge/phono amp
For anything digital, it’s all about the DAC
if you start with these, you csn always upgrade the rest but if you don’t have a good source it will sound terrible
In my opinion and experience, the room is the most important. If the room is bad, no speaker will make it sound good. If the room is decent, then the speakers are always the most impactful component of the stereo itself.
For all three sources, CD, Vinyl, Digital streaming, you first have to make sure the source material has a DECENT level of quality. For example, music over wifi rather than bluetooth is a pretty good level that i can be happy with most of the time. CD player at least perhaps in the $300 range? something decent but not great will have acceptable sound. For Vinyl, i have zero personal experience - i have a feeling you need to spend at least $500 to get decent turntable, and maybe $200 for cartridge, once again i have no idea, but vinyl is likely the most expensive.
Next, once your source is DECENT, (which you haven’t told us maybe you are already up to this point) i would make the BIG upgrade in the Speakers first. Amp second. Definitely NOT cables. IF you have all separate components then preamp probably equally important as the amp, but i choose to stick with INTEGRATED amp, so once again, nothing to say here.
Speakers and amp… buy a tube amp if you have high efficiency speakers